This invention relates to compressors for use in air conditioning systems for automotive vehicles, and more particularly to compressors which themselves are capable of interrupting discharge of pressurized gas and controlling the discharge rate of same.
Compressors for use in air conditioning systems for automotive vehicles or like systems generally include rotary compressors and reciprocating compressors. In these compressors, transmission of torque from a driver to the compressor is carried out by means of a pulley or a gear which is mounted on the main shaft of the compressor for rotating the rotor in the case of a rotary compressor or on the crank-shaft connected to the piston in the case of a reciprocating compressor. A clutch is provided between the driver and the main shaft of the compressor or the crank-shaft, which operates to permit or interrupt transmission of torque from the driver to the compressor, to make it possible to interrupt the operation of the compressor whenever discharge of pressurized gas is not required.
This clutch usually comprises a magnetic clutch which is arranged for engagement or disengagement in response to the action of a thermostat which is arranged to detect the compartment temperature.
A compressor having the above arrangement, when used in an air conditioning system for automotive vehicles, is mounted within the engine room of the vehicle and is driven by part of the output of the engine in such a manner that torque is transmitted from the engine to the input pulley of the magnetic clutch by means of a belt connected between the above input pulley and a pulley mounted on the crank-shaft of the engine.
However, the conventional compressors, which are provided with magnetic clutches for torque transmission to the compressor and interruption of same, have the disadvantage that the engine undergoes an increased load due to the facts that the diameter of the input pulley of the magnetic clutch cannot be designed moderately small owing to the structural limitation of the magnetic clutch and the weight of the magnetic clutch is considerably large.
Further, in air conditioning systems in general, when there is an increase in the rotational speed of the compressor during normal operation, the compressing capacity of the compressor increases in direct proportion to the increase of the rotational speed of the compressor. However, most of the currently used air conditioning systems for use in automotive vehicles have a maximum refrigerating capacity of approximately 3,000 kcal/H. Therefore, even though the compressor has its compressing capacity increased with the increase of the rotational speed of the compressor, the air conditioning system cannot exhibit a refrigerating capacity of a calorific value exceeding the above value. Therefore, it is necessary to restrain an increase in the refrigerating capacity of the compressor when the compressor speed has exceeded a certain level, to ensure a long effective life of the air conditioning system.